Embodiments of the present invention generally relate to an apparatus and method for performing an ion concentration analysis in a liquid crystal display (LCD) panel.
With the continuous advancements in technology, liquid crystal display (LCD) devices, which have advantages of smaller volume, lighter weight, lower power consumption and lower radiation, have been replacing cathode-ray tube (CRT) devices in the market and been widely used in television sets and computer display applications. LCD devices can generally be classified into three types, i.e., the thin film transistor (TFT) type, the twisted nematic (TN) type, and the super twisted nematic (STN) type. As one of main parts of a LCD device, a liquid crystal display panel comprises a color filter substrate, a thin film transistor (TFT) array substrate, a liquid crystal layer sealed between the two substrates, a sealant member, alignment layers and etc.
Concentration of ions contained in an LCD panel is critical to the electrical characteristics of the LCD panel. Ion concentration affects performance of the LCD panel in various aspects, such as voltage remaining level, threshold voltage value, flicker, image sticking and the like. For this reason, ion concentration needs to be controlled during manufacture of the LCD device. For example, in the liquid crystal layer of a TN-type LCD device, the concentration of cathode and anode ions should meet the specification that the highest concentration of anode ions is no more than 0.5 ppm and the highest concentration of cathode ions is no more than 100 ppm.
Conventionally, ion concentration is detected through chemical analysis methods such as ion chromatography. Chemical analysis methods can be employed to compare ion concentrations in two LCD panels and determine which alignment layer may introduce ions more easily according to the comparing result. Ion concentration detection by chemical analysis can advantageously determine composition of the ions and obtain concentration value of each kind of ions. The chemical analysis method is effective in ion concentration analysis and microscopic analysis, but it still has disadvantages. In conceiving the present invention, the inventor found the chemical analysis has at least following disadvantages.
(1) The LCD panel subject to analysis must be disassembled to perform the chemical analysis, thus the LCD panel cannot operate or undergo other analyses any more.
(2) The chemical analysis method usually takes a long time.
(3) Since many ions are absorbed on surface of the alignment layer in the LCD device, the chemical analysis, which mainly detects ion contents in the liquid crystal layer, can only involves a part of ions in the LCD panel.
(4) The chemical analysis method cannot obtain the total ion content in the LCD panel directly, it can only analyses ion concentration in term of one of the liquid crystal layer, the alignment layer, the sealant and the manufacture process, respectively, and it is difficult to integrate the analysis results.